Receiving apparatus for electro



Oct. 15, 1935. Q Q LAURiTSE-N Re. 19,723

RECEIVING APPARATUS FOR ELECTROMAGNETIC WAVES Original Filed May 9, 1923 INYENTOR 7 A ORNEY U sirable property Reissued Oct. 15, 1935 UNITED STATES PATENT OFFICE RECEIVING APPARATUS FOR ELECTRO- MAGNETIC WAVES Charles C. Lauritsen, Pasadena,

by mesne assignments, to Radio Calif., assignor, Corporation of Serial No. 637,641, May 9, 1923.

Application for reissue July 31, 1935, Serial No. 34,117

5 Claims.

It is a well known fact that the simple receiving apparatus now in common use in radio telephony, (for example receiving sets of the single circuit type) lack, to a great extent, the deof selecting a desired signal to the exclusion of signals of other frequencies. Also a great deal of annoying interference with reception on nearby receiving sets is caused by radiation from tube receiving sets when regeneration, or what is commonly known as the feedbac circuit is employed.

One of the objects of this invention is to secure sharp tuning and consequent elimination or reductlon of undesired signals and other "interference" by simple means requiring minimum adjustments.

A further object and advantage of the invention is to prevent, or so decrease radiation from tube receiving sets as to eliminate interference between adjacently located sets.

The objects of my invention are accomplished without making it necessary to depart from the antenna height and dimensions most suitable for the collection of sufficient signal energy.

In the accompanying drawing Figure 1 diagrammatically illustrates receiving apparatus of the regenerative type embodying my invention; Figure 2 illustrates a modification of the arrangement shown in Figure 1, regeneration being omitted, and Figure 3 shows another modification, also without regeneration.

Referring to Figure l the collector system comprises the antenna l and ground connection 2, which are connected as shown to a closed oscillatory circuit comprising the condenser 3 of comparatively large capacity, the condenser 4, and the inductance 5. As shown, the connections of the antenna and ground to this closed oscillatory circuit are so located that the circuit has two branches between the antenna and ground connectlons, one containing the capacity 3, and which is hereinafter referred to as the by-pass" branch, and the other the capacity 4 and inductance 5, hereinafter referred to as the signal receiving" branch.

The vacuum tube T has its grid electrode 6 and filament electrode 1 directly connected to points on the signal receiving circuit on opposite sides of the inductance 5, whereby the drop of signal potential across the inductance is impressed upon the grid circuit of the tube. This grid circuit may, as is common practice, include the grid condenser 13 and grid leak l4. Filament current is supplied from battery A controlled by rheostat 12. The plate circuit of the tube comprises battery B, telephones l0 shunted by condenser ll, tickler coil 9 in inductive relation with coil 5, and the plate electrode 8 of the tube.

The circuits illustrated in Figure 2 differ from those of Figure 1 only in that the tickler coil 9 is omitted from the plate circuit and the grid circuit of the tube is connected across the terminals of the capacity 4 of the closed oscillatory circuit in the collector system instead of across the inductance 5.

The circuits of Figure 3 correspond to those of Figure 1 except in the omission of the tickler coil 9 and the substitution of resistance or inductance 15 for condenser 3 in the oscillatory circuit.

It will be understood that while, in the drawing the detector circuit is shown directly connected to the collector system, one or more stages of amplification may be employed prior to detection, the grid circuit of the first amplifying tube being connected to the collector system in the same manner as the detector circuits are connected in the illustrations.

The elements of the closed oscillatory circuit in the collector system are proportioned to produce a stiff circuit, the resistance being low and the ratio of inductance to capacity being high. A suitable value for the inductance is 0.250 millihenrys (250 micro-henrys), and that for condenser 3 is .061 microfarad. I condenser 4 is variable and a suitable maximum value is .0003 microfarad. The value normally employed will of course be less than the maximum, and it is preferable that the maximum capacity of 4 be less than that of 3.

By adjustment of the variable condenser 4, or the inductance 5, or both, the oscillatory circuit is rendered resonant to the desired signal wave length and is capable of being made resonant to what are usually referred to as short wave lengths, that is to say, of 600 meters and shorter. Being a stiff circuit a given adjustment of the condenser 4 renders the circuit resonant to an extremely narrow band of frequencies and the condenser 3 acts as a by-pass from antenna to ground for all other frequencies. As indicated in Figure 3 a resistance or an inductance may be substituted for the capacity in the by-pass branch. In the claims these three classes of elements are referred to as impedance. I prefer to use a con denser in the by-pass branch because of its inherent characteristic of ofiering a lower resistance to higher frequencies, such as 200 meter spark waves and certain types of static.

When regeneration is employed as indicated 'he capacity of ground will be only a small fraction E. M. F. in the circuit. The amount of energy radiated from the antenna will, therefore, be proportionately small, and as this is equivalent to cerned, ing, and that where reference is made in the description and claims to adjusting the closed 0sciliatory circuit to resonance with signals of the frequency to be received, I mean that the elements of this circuit are so adjusted that in cooperation with the above factor a tuned system is produced which is resonant to signals of the frequency to be received. In other words, this antenna to ground capacity constitutes a part of the capacity of the closed oscillatory circuit from the standpoint of the tuning referred to.

I am aware that modifications in the type of appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. Receiving the impedance in the by-pass branch, and means associated with the signal receiving branch for detecting the received signals.

2. Receiving apparatus for electromagnetic Waves comprising a collector circuit and a closed oscillatory circuit connected in the collector circuit in such manner that one portion of the oscillatory circuit constitutes a by-pass branch and the other tance and capacity elements ad usted to render the oscillatory circuit resonant to signals of the impedance path than exists through the signal receiving branch, and means associated with the signal receiving branch for detecting the received signals.

4. A receiving apparatus for electromagnetic waves comprising an antenna, a closed oscillatory circuit comprising an inductance, a condenser branch containing the impedance, the impedance branch to said signal currents of ing branch, and signal receiving means associated with the signal receiving branch.

5. A receiving apparatus for electromagnetic waves comprising an antenna, a closed oscillatory CHAS. C. LAURITSEN. 

